Hydraulic motor



Dec. 19, 1933. v w. FERRIS ET AL 1,939,887

HYDRAULIC MOTOR Filed July 28, 1950 4 Sheets-Sheet l WALTER F'EF@ HHS. JAMES KIJDUGLLAS.

Dec. 19, 1933. w. FERRls Ef AL HYDRAULIC MOTOR rFiled JulyQB, 1930 4 Sheets-Sheet 2 l gwuvmtow 'WALTER FEHFHS. JAMES K-DDL1ELAS. a?? 7 F chrom,

Dec. 19, 1933. w. FERRls' Er AL 1,939,887

HYDRAULIC MOTOR Filed July 28, 1930 4 Sheets-Sheet 3 j 5? i- EN l I IJ g l w x L# d f WAL-TEF( @Wim my I dem,

.JAMES K.DULJELAS.'

Dec. 19, 1933.

w. FERRIS ET AL HYDRAULIC MOTOR Filed July 28. 193C 4 Sheets-Sheet 4 gmx/nto@ WALTER FERRE. ...JAMES K.D1:|.\ |ELAS.

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Patented Dec. 19,- 1933 UNITED STATES PATENT ori-ICE HYDRAULIC MOTOR Walter Ferris and James K. Douglas, Milwaukee,

Wis., assignors to The waukee, Wis., a corpora Oilgear Company, Miltion of Wisconsin Application July 2s, 1930. serial No. 471,254 1s claims. (cl. 121-122) This invention relates to hydraulic motors.

hydraulic motor to which Y sued February-16, 1932 to Walter Ferris.

An object of the invention is to cause one driving arm to exert a rotative force upon the wheel beforethe other driving arm ceases to exert a rotative force thereon'to thereby obtain a'practically uniform rate of rotation from the intermittently acting driving arms.

4Another object Iis to utilize expansive forces existing in one cylinder and driving arm to bring the other Adriving arm intoe operation.

Another object is toavoid any lost motion between the dri-'ing arm lbearing between the driving arm and its piston.

Another object is to eliminate all objectionable noises. f

Another obect is to provide a'hydraulic motor of this character which will operate smoothly and evenly and which is 'susceptible of close control.

to be retracted so that the ative cylinder and the expansive r'forces built'up by that pressure in the cylinder walls, the piping,

the driving arm and associated parts assist the `the driving arms, and

the plunger of the been advanced ya. mitted the pilot valve to close.

.hydraulic motors lis adjusted by forces outside disengagcs a tooth of the wheel, a rolling thrust connection between the driving arm and its piston, means for quickly and positively reversing a valve operating mechanism which is operated bythe movement of the ,60 driving arm.

A hydraulic motor embodying the invention is illustrated in the accompanying drawings in which the views are as follows:

Fig. l is a top plan view with a part o1' the top 65 cover plate removed.

Fig. 2 is a side view partly in elevation and partly in section.

Fig. 3 is a detail view showing the position occupied by one of the driving arms just after it is fully retracted and before it actuates the valve operating mechanism as shown in Fig. 2.

Fig. 4 is a detail of a buffer.

Fig. 5 is a schematic .drawing of the hydraulic circuit. Fig. 6 is a view similar to Fig. 5 but showing control valve at an intermediate point in its travel at which point the two power cylinders are in communication with each other and with 'the pump.

Fig. 7 is a detail view somewhat similar to Fig. 3 but showing the driving arm after it has short distance and has per- Fig. 8 is a detail View showing the driving arm 85 ing retracted but before it reaches the position shown in Fig.f3.

The motor is provided with a closed housing 1 which encloses and supports the working parts thereof, a power shaft 2journaled in bearings 3 90 carriedby the side walls of the housing 1, al ratchet wheel 4'1lxed upon the shaft 2, driving arms 5 and 6 for rotating the ratchet wheel 4, 7 and 8 for operating the arms control valve 9 for `controllingi 95 driving liquid to the motors 7 5 and 6, and a the delivery of and 8.

'Ihe driving liquid is supplied from a positive displacement pump 10 which is shown attached to the housing 1 and which, preferably, is regu- 100 latable to vary the rate of its delivery to therebyu vary the speed of the motor. The pump 10 is a well-known type which delivers liquid at a constant volume until its regulating mechanism of the pump itself. As such pumps are well` known, the pump 10 has not been illustrated nor described in detail herein. A pump which may be employed for this purpose is disclosed in Patent No. 1,753,562 issued April 8, 1930 to John P. Ferris, but the ,110

' tion.

The teeth of the ratchet wheel 4 are capable of withstanding the thrust of the driving arms 5 and 6 and have rolling contact with driving arms 5 and 6, thus causing the free or contact ends of the arms 5 and 6 to roll upwardly as the wheel 4 is rotated and thereby eliminate substantially all friction between the arms and the ratchet teeth.

' Preferably, the ratchet teeth consist ofA round bars 12 which are evenly spaced around a circle concentric to the axis of the shaft 2 and divided into two series. The outer ends of each series of bars 12 are anchored in a disk 13 and the inner ends thereof are anchored in a disk 14. The

disks 13 and 14 are carriedby a hub 15 which is` rigidly secured to the shaft 2 or formed integral therewith. A

The motors 7 and`8 have the pistons 16 and 17 thereof arranged, respectively, in cylinders 18 and 19 and provided with rods 20 and 21 to which the driving arms 5 and 6 are connected.

Each of the piston rods 20 and 21 is provided at its forward end with a slot 22 to receive the rear end of its associated driving arm which is pivotally' secured therein by a pivot 23 and provided upon its rear end with an arcuatecontact face 24 to abut a bearing face 25 formed by the bottom of the slot 22.

Each pivot 23 is fixed in the piston rod and extends through a hole 26 which is formed in the end of the driving arm and is larger than the pivot 23 so as to enable the face 24 to bear against the face 25 during the working stroke and, when the forward end of the driving arm is raised by the rolling engagement between its face 11 `and apply force to the one of the bars 12, to enable the arcuate contact face 24 to rock upon the face 25 and thereby eliminate substantially all friction between the same. During this movement, the pin 23 does not engage the -side walls of the'hole 26.

The bars 12 in one series are engaged in succession by the driving 'arm 5 and the bars 12 in the other series are engaged in succession by the driving arm 6, the motors 7 and 8 are operated to advance the driving arms alternately, and one driving arm engages a bar 12 and starts applying force-thereto before the other arm ceases to bar 12 with which it is engaged. Consequently a continuous rotative force is applied to the shaft 2 and each arm falls as soon as it ceases to apply force to thebar 12 with which itis engaged.

The downward movement of the driving arm is limited by a stop 27 which overhangs the face 11 andengagesthe bar 12 as soon as the face 11 is disengaged therefrom and thereby supports the driving arm as it is being retracted.

In order to cushion the fall of the driving arms and to thereby prevent them from rebounding,

each stop 27 is provided with a bore 28 which ex- Fig. 4.

The upper end of the bore 28 is closed by a shallow reservoir 29 from which liquid may ilow into the bore 28 through a relatively large passageway 30 which extends vertically through the bottom of the reservoir 29 and is controlled by a check valve 31. When the butler is operated, the .check valve31 closes the passageway 30 and the liquid is expelled from the bore 28 through a relatively arcuate faces which make athe contact faces 11 of the.,

small passageway 32 which extends through the bottom of the reservoir 29.

The bore 28 has a plunger 33 `fitted therein and urged downward .by a helical compression spring 34, and the lower ends of both the bore and the plunger are reduced in diameter to limit the downward movement of the plunger. l

When the forward end of the' driving arm'falls, the plunger 33 strikes the bar 12 which has just been disengaged from the face 11. The impact forces the plunger 33 into the bore 28 and tends to eject liquid through the passageway 3() but the check valve 31 closes and the liquid is ejected through the small passageway 32, thereby cushioning the driving arm and rebounding.

The spring 34 is employed to insure that the plunger 33 returns to its initial position after it and the bar 12 have moved out of engagement with each other. The strength of the spring 34 is small relatively to the force developed by the falling arm so that the fall of the arm is cushioned almost exclusively by the liquid in the cylinder 28.

Thev rearward movement of the `driving arm and the rotation of the ratchet wheel carries the bar 12, which has just been disengagedfrom the face 11, along the underside of the stop 27 until a face 35, which is formed on the underside of the driving arm and joined to the face 11 by a face 36, is engaged by the next bar in that series which in turn supports the forward end of the driving arm.

Continued rearward movement of the free driving arm .and continued rotation of the ratchet wheel causes the bar 12 to move forwardly along preventing it from the face 35 until it engages theface 36 and then the weight of the driving arm causes the face 11 to ride downwardly upon the arcuate face of the bar 12 and produce a wedging action which moves the face 24 against the face 25 without appreciable impact.

To effect this continuous wedging action, the

arcuate face llis formed with a radius centering in a point 37 so located that the length of the driving arm between'the face 11 abutting against i a b ar 12 and the-face 24 abutting against face 25 will gradually increase as the face 11 slides downwardly in contact with the bar 12 during the descent ofthe driving arm.

Liquid from the pump 10 is directed to the two motors '7 and 8 alternately bythe control valve 9 which has a plunger 38 fitted in its cylinder 39 and provided with two pistons 40. and 41 for controlling two ports 42 and 43, respectively. The port 42 is connected by a duct 44 to the rear end of the motor cylinder 18, the port 43 is connected by a duct 45 .to the rear end of the motor cylinder 19, and a port 46 arranged intermediate the ports 42 vand 43 is connected by a pipe 47 to the discharge outlet of the pump 10.

Liquid is returned to the pump 10 through the ducts 44 and 45, the control'valve 9 and a return pipe 48 which has one end connected to the reservoir of the pump 10 and'its other end divided into two branches and connected to two cham bers 49 and 50 arranged in the ends of the valve cylinder 39.

The valve plunger .38 is reciprocated by. two pistons 51 and 52 which are arranged, respectively, in cylinders 53 and 54 connected to the ends of the valve cylinder 39.

'I'he pistons 51 and 52 are actuated by liquid supplied from a low pressure pump 55, shown diagrammatically as being a gear pump, which is ordinarily incorporated in the pump- 10 to supercharge the saine, as disclosed'in Patent No. 1,753,562 referred to above. The pumps 10 and 55 are protected, respectively, by a high pressurev relief valve 56' and a low pressure relief valve 57 which, ordinarily, are also incorporated in the pump. 10 as regular parts thereof.

'Ihe delivery of liquid from the gear pump 55 to the cylinders 53 and 54 is controlled by two pilot valves 58 and 59 which are arranged immediately below the motors 7 and 8 respectively. Each of the pilot valves 58 and 59 has a -plunger 60 arranged in its casing to control cominunication between two ports 61 and 62 and between the port 61 and a drain pipe 63 which connects the rear end of each pilot valve to the returnpipe 48. The ports 62 of both pilot valves are connectedby a pipe 64I to the gear pumpA 55, the port 61 of the valve 58 .is connected by a. pipe 65` to the cylinder 54, and the port 61 of the valve 59 is connected by a. pipe 66 to the cylinder 53.

Each of the valves 58 and 59 has a helical compression spring 67 arranged therein which urges the plunger 60 forwardly to close com# munication between the ports 61 and 62 and to open communication between the port 61 and the drain pipe 63.

The plunger` 60 of the valve 59 is adapted to be forced. rearward against 'the action of the spring 67, to open communication between the ports 61. and 62 and to close communication between the port 61` and the drain pipe 63, by the lower end of an actuating lever 68 which is pivoted intermediate its ends to the driving arm 6. The lower end of the lever 68 is urged rearward by a tension spring 69 which has `one end attached to the driving arm 6 and its other end attached to the upper end of the lever 68.

As the driving arm approaches the limit of its rearward stroke, a projection 70 on the lower end of the lever 68 engages an abutment 71 which is pivoted to the end of the cylinder 19 and is free Yto swing forward but is held against `its pivot against the swinging rearward. The lower end of the lever 68 is thus held temporarily against further rear-- ward movement, and continued retraction of the driving arm 6 causes the lever 68 to swing upon action of the spring 69 as Shown in Fig. 3. y

After the piston 17 has stalled at the end ofu its rearward stroke and when the face 11 on the driving arm 6 has moved downward across the face of thelbar 12 a predetermined distance, the projection 70 passes out of engagement with the abutment 71 and the spring 69 swings the lever 68 upon its pivot and forces the plunger 60 rearward against the resistance of the spring 67as shown in Fig. 2. The rearward movement of the lower end of the lever 68 is limited by an adjustable stop 72 which iscarried by the arm 6 to engage the upper` end o f the lever 68.

As the pilot valve 58 is operated in exactly the same manner and by mechanism identical to that just described, the corresponding parts of return pipe 48.

the two mechanisms have been indicated by the same reference numerals.

In order that an adequate supply of liquid may be available at all times for operating the valve 9 with the requisite promptness to insure quick reversals at a uniform speed regardless of changes in rate'of movement of the valve gear parts, an accumulator 73 is connected into the supply' pipe 64, and the gear pump 55 delivers liquid thereto which depresses its piston 74 against the action of a spring 75, thus storing a quantity of liquid at gear pump pressure to supplement the volume of liquid delivered by the gear pump and providing a reservoir of energy suflicient to move the valve plunger 38 uniformly under all conditions. Liquid which may leak past the piston 74 is returned to the pump 10 through a pipe 76, the drain pipe 63 and the When the plunger 60 of the valve 59 is moved rearwardly to open communication between the ports 61 and 62, liquid from the gear pump 55 and/or the accumulator 73 flows through the pipe 64, the pilot valve 59, the pipe 66, a duct 77,aspring check valve 78 and into the cylinder 53, causing the piston y51 to advance into the chamber 49 and move the valve plunger 38 axially to open communication between the ports 43 and 46 and to move the piston 52 into the cylinder 54, as shown in Fig. 5.

The duct 77 communicates with the outer end communicates directly with an annular port 79 which is arranged intermediate the ends of the cylinder 5 3.

The piston 52 and the cylinder 54 are identical, respectively, to the piston 51 and cylinder 53 and function in exactly the same manner. Consequently, like parts have been indicated by like reference numerals.

When the liquid enters the cylinder 53 and forces the. piston 51 inwardly to move the valve plunger 38 and the piston 52 axially, liquid is expelled from the cylinder I54 through the duct 77, the pipe 65, the' pilot valve 58 and the drain pipe 63 to the return pipe 48. r.

During the `rst part of the piston movement, the liquid flows freely from the cylinder 54 through the port 79 and into the duct 77, and the valve plunger 38 moves at high speed but, as soon as the end of the piston 52 passes the edge of the port 79, the check valve 78 causes the liquid to be expelled from the cylinder 54 through a number of tapered grooves 80 which are formed in the end of the piston 52. The effective area of the groovea 80 gradually decreases as the piston 52 moves outwardly and the plunger 38 is thus decelerated until the grooves 80 are entirely out of registry with the port 7-9 and the remaining liquid is trapped in the outer end of the cylinder 54, thereby bringing the plunger 38 and thepistons 51 and 52 to a complete stop without shock or impact.

The speed at which the valve plunger 38 moves is dependent upon the volume of liquid delivered tothe cylinders 53 and 54 through the pipes K(6,5 and.66 and, as the accumulator 73 provides a supply of driving liquid in excess of the require- 'ments of the valve 9,. the speed of the plunger 38 is controlled by providing pipes 65 and 66 of the correctrcrossfsectional area to deliver the exact volume v, of'liquid required to move the plunger 38 at the desired speed.

After the valve -9 has been operated and its plunger 38 is in the position shown' in Fig.'5,

'the pipe 64, and

liquid is delivered by the pump 10 through the pipe 47, the valve cylinder 39 and the duct 45 to the rear end of ,the moto/1- cylinder 19, thereby forcing the piston 17 forward to advance the driving arm 6 and impart rotation to the ratchet wheel 4 and the power shaft 2.

Forward movement of the driving arm 6 moves the lower end of the lever 68 out of engagement with the stem of pilot valve59 and allows the spring 67 to move the plunger 60 to its initial position.

The liquid in the forward end of the motor cylinder 19 is expelled through a pipe 8l into the motor cylinder 18 and forces the piston 16 rearward to retract the driving arm 5.

At the same time, the gear pump 55 is delivering an additional limited volume of liquid through the pipe 64, a pipe 82, a. choke 83 and the pipe 81 into the forward end of the motor cylinder .18 to retract the piston 16 and the driving arm 5 faster than the piston 17 and the driving arm 6 advances, and to insure that piston 16 is fully retracted and stalled against the head of'cylinder 18 before piston 17 completes its working stroke. When the driving arm 5 starts rearward, its contact face 11 disengages the bar 12 with which it was in contact and the forward end of the driving arm falls, the plunger 33 strikes the bar 12 and cushions the fall of the driving arm, and then the stop 27 supports the driving arm 5 until the driving arm 6 has rotated the ratchet wheel 4 suinciently to bring the next bar 12 into engagement with the face 35 to support the driving arm 5 as shown in Fig. 8:

The impact caused by the buifer plunger 33 striking the bar 12 causes liquid to be ejected through Athe restricted passageway 32 and into the reservoir 29, as previously described. When the plunger 33 moves out of engagement with the bar 12, its own weight and the pressure exerted by the spring34 moves it downward and liquid flows into the bore 28 through the passageway 30 from the reservoirv 29 which is supplied with liquid from the pipe 64 through a pipe 84 having a choke or valve --85 arranged therein to limit the now of liquid therethrough.

When the piston 16 reaches the limit of its rearward stroke and stalls against the end of the cylinder 18, the li uid expelled from the forward end of the cylii er 19 during the remainder of the working stroke of the piston 17 passes through the pipe 81, a relief valve 86 and a pipe 87 into the drain pipe 63. j

Thedriving arm 5 is now standing idle momentarily while the driving arm 6 rotates the' ratchet wheel 4 and moves `,the bar 12 along the vfaces 35 and 36 on the driving arm 5 and into engagement with the Fig. 7, thereby enabling theiorward end of the driving arm 5' to descend until theprojecticn 70, thereon'passesbelow the abutment 71 and' the spring 69 swings the lever 68-to operate the valve 58, as previously described. y

The cylinder 54 is now open to gear pump pressure through the pipe 65, the valve 58 and the sudden rush 'of liquid from the gear pump 55 and-the accumulator 73 forces the piston 52-inward at high speed to operate the valve plunger into the cylinder 53 where its momentum is nrst checked and then the piston-and plunger are brought to-rest by the liquid trappedin the 'outer end of the cylinder 53as explained in connection with. the piston 52and the cylinder 54. The rapid traverse o! the piston 51 causes the face 11 therepn, as shown in 3'8 and move the piston 51 -nquid in the pipe es, the valve 5s, the pipe es and the pipe 48 to move at high speed and, when the piston 51 closes the port 79, the momentum of this liquid creates a vacuum which causes the liquid to rebound. If the check valve 73 opened freely, the rebounding liquid would enter the outer end of the cylinder 53 and force the piston 51 inward and move the valve plunger 38.

Forv this reason, the spring check valve 78 is adjusted -to resist a pressure greater than fteen pounds per square inch to prevent the rebounding liquid from entering the cylinder 53, thus functioning asv a hydraulic detent for holding the plunger 38 in position. The other check valve 78 functions in exactly the same manner.

As the plunger 38 moves from one position to the other, the cylinders 18. and 19 are brought into communication momentarily with each other and with the pump 10, as shown in Fig. 6, by means of( notches 88 which are formed in the inner f of the pistons 40 and 41 on the plunger 38, whereby liquid from the pump 10 is delivered simultaneously to bothv cylinders to cause the driving arm 5 to exert force upon the ratchet wheel 4 before the driving arm 6 ceases to exert force thereon.

The motor is ordinarily operated with a liquid which is slightly elastic, such as lubricating oil, and the pressure built up by thepump 10 in advancing the piston 17 compressesthe liquid and sets up stresses in the cylinder, pipes and driving arm. f

When the two motor cylinders 18 and 19 are brought into communication with each other through the notches 88, the energy thus stored and particuarly the expansive force stored in the large volume of liquid in the motor cylinder 19 is utilized for starting the driving arm 5 on its power stroke before the driving arm 6 ceases to apply rotativeforce to the wheel 4.

The volume of liquid behind the piston of the motor which is completing its'working stroke, the length and 'depth of the notches 88 and the speed oi' the valve plunger 38 bear a definite relation to one another and are so proportioned that the force transmitted to the ratchet wheel by the driving arm about to be advanced increases as the force transmitted to the ratchet wheel by the other arm decreases so that a substantially uniform force is exerted at all times uponthe ratchet wheel by either one or both of the driving arms.

The motors 7 and 8 are operatedv alternately, and thedrivingarm 6 is retracted in the same manner as justkdescribed. The cylinders 18 and 19 are\incommunication with each othe and withthe pump 10 at each end of each stroke of the drivingl arms? one or both of the driving arms are exerting force upon the wheel 4 at all times and, due to the arcuate faces 11 and 24,

each driving arm is wedged between the piston rod of its motor and a bar 12 before it starts to advance. Consequently, the power .shaft 2 is rotated at a uniform and constantspeed.

The -invention herein set forth is susceptible voi various modifications and 'adaptations without departing from the scope thereof as hereafter claimed.

We claim:

1. A motor, comprising a ratchet wheel, two reciprocal driving arms for engaging said wheel alternately upon the same side thereof to impart rotative force thereto, a piston and a cylinder connected to each arm for advancing and retracting it alternately with the advance and retraction ofl nadas? the other arm, means for supplying pressure liquid the rear or pressure ends of said cylinders alternately to advance said arms alternately and retract one arm as the other arm advances and to cause the retracting arm to reach the end of its vancing arm reaches the end of its advance stroke, a valve included recting liquid to the pressure ends of said cylinlliquid to the rear energy to said 4. A motor, reciprocable driving arms for engaging said wheel or pressure ends of said cylinders alternately to advance said arms alternately and cause the same toapply rotative torce to said return stroke before the adin said supplying means for dicomprising ya ratchet wheel, two

' S wheel, means for delivering liquid to the front end of each cylinder-to retract one arm as the other y. 6. A motor, comprising a 'ratchet wheel, two reciprocable driving arms for engaging said -wheel alternately upon the same side thereof to supplying means for ceases to apply rotative force thereto, hydraulic means foroperating said valve, an accumulator connected in circuit with said hydraulic means for accelerating the operation of said control valve, and means including a pilot valve for controlling said hydraulic means.

8. A motor, comprising a ratchet wheel, two reciprocableA driving arms for engaging said Wheel alternately upon the same side thereof to impart rotative force thereto, a piston and a cylinder connected to each arm for advancing and retracting it alternately with the advance and retraction of thev other arm, means for supplying pressure liquid to the rear or pressure ends of said cylinders alternately to advance said 'arms alternately and cause thesame to apply said cylinder to a source of rotative force to said wheelfmeans lfor delivering liquid to the front end of each cylinder to retract one arm as the other arm advances and to cause the retracting arm to reach the end of its return stroke before the 'advancing arm reaches thebendof its advance stroke, a valve included in said supplying means for directing liquid to the pressure ends of said cylinders alternately and having means for connecting said pressure ends together momentarily to cause each of said arms to apply rotative force to said wheel before the other arm ceases to apply rotative force thereto, hydraulic means for operating said valve, an accumulator connected in circuit with said hydraulic means for accelerating the operation of said control valve, pilot valves for controlling said hydraulic means, and spring actuated means for operating said pilot valves.

9. In a hydraulic motor, the combination with a ratchet wheel, a power cylinder having its axis substantially tangential to said wheel, a piston arranged in said cylinder, means foi connecting driving liquid, means included in said connecting means for controlling 'the delivery of liquid from said source to said cylinder to thereby cause rocated, and a driving piston and said piston to be reciparm reciprocated by said adapted to engage the teeth ofv said succession and thereby impart rotation to said wheel as said arm is reciprocated,

of arcuate faces on the teeth of said ratchet wheel ardmovemcntotsaidarm carried by said Athe delivery of liquid wheel alternately rocated, and a driving arm reciprocated by said piston and adapted to engage the teeth of said ratchet wheel in succession and thereby impart rotation to said wheel as said arm is reciprocated, of arcuate faces on the teeth of said ratchet wheel for providing a rolling contact with said armv to raise the contact end of said arm as said wheel rotates, a' stop arranged upon the contact end of said arm and overhanging a tooth of said wheel for limiting the downward movement of said arm after the contact end thereof has disengaged one of said teeth, and a hydraulic buffer stop for engaging said teeth to cushion'the fall of said arm.

11. In a hydraulic motor, the combination with a ratchet wheel, a power cylinder having its axis substantially tangential to said wheel, a piston arranged in said cylinder, means for connecting said cylinder to a source of driving liquid, means included in said connecting means for controlling from said source to said cylinder to thereby cause said piston to be reciprocated, and a driving arm reciprocated by said piston and adapted to engage the teeth of said ratchet wheel in succession and thereby impart rotation to said wheel as said arm is reciprocated, of arcuate faces on the teeth of said ratchet wheel for providing a rolling contact with said arm to raise the contact end of said arm as said wheel rotates, a stop arranged upon the contact end of said arm and overhanging a tooth of said wheel fos limiting the downward movement of said arm after the contact end thereof has disengaged one of said teeth, a hydraulic buiIer carried by said stop for engaging said teeth to cushion the fall no of said arm, a reservoir carried by said buffer for supplying the same with liquid,'and means for substantially tangential to said wheel, a piston arranged in said cylinder and provided with a piston rod extending from said cylinder, means for connecting said cylinder to a source of driving liquid, means included in said connecting means for conm trolling the delivery of liquid from said source to said cylinder to thereby cause said piston to be reciprocated, and a driving arm connected'by a lost-motion connectionto said piston rod and reciprocated thereby to engage the teeth of said ratchet wheel in succession and thereby impart rotation to said wheel as -said arm is reciprocated,

of a bearing surface arranged upon saidpiston f rod independent of said lost-motion connection, A' anarcuat'e face arranged upon the rear end of 130 said arm to abut saidsrface and thereby take the thrust of said piston and provide a'rolling contact between said arm land said piston rod,

o! said ratchet wheel wheel for limiting the downward movement of said arm after the contact end'thereofhas disengaged one of said teeth.

13.'Amowr,

to impart rotative force thetel cylinder connected to each it alternately to,apistonanda armforadvancingand withsaidarmto to advance said arms, alternately and cause the same to impart rotative force to said wheel, means for delivering liquid to the front end of each cylinder to retract one arm as the other arm advances and to cause the retracting arm to reach the end of its return stroke before the advancing arm reaches the end of its advance stroke, a control valve included in said supplying means for directing liquid to the pressure ends of said ,cylinders alternately and having means for connecting said pressure ends together momentarily to cause each arm .t apply rotative force to said wheel before the other arm ceases to apply rotative force thereto, hydraulic means for operating .said valve, means for supplying liquid to said hydraulic means and for controlling the operation thereof, an accumulator connected in circuit with said hydraulic means for accelerating the operation of said valve, and means for preventing lost motion between said pistonand said ratchet wheel.

14. In a hydraulic motor, the combination of a ratchet wheel, a power cylinder having its axis substantially tangential to said wheel, a piston arranged in said cylinder,means for connecting said cylinder to a source of driving liquid, means for controlling the delivery of liquid from said source to said cylinder to thereby cause said piston to be reciprocated, a driving arm loosely pivoted at its rear end to said piston and reciprocated thereby to engage the teeth of said ratchet wheel in succession and thereby impart rotation to said wheel as said arm is reciprocated, an arcuate'face on the rear end of said arm abutting a surface on said piston to takev the thrust of said piston, arcuate faces on the teeth of said ratchet wheel for providing a rolling contact with said arm to raise the forward end thereof as said wheel rotates, a stop arranged'uponvthe forward end of said arm and overhanging a tooth of said wheel for limiting the downward movement of said arm after its forward end has disengaged one of said teeth, and an arcuate face on the forward end of said arm for engaging a tooth of said wheel to wedge said arm rearwardly against said piston and thereby enable the arcuate face on the rear end of said arm to rock upon said surface on said piston.

15. A motor, comprising a ratchet wheel, .two

reciprocable driving arms for imparting` rotative force to said wheel, a piston and a cylinder for `driving of said arms, a valve .casing connected to said driving cylinders and to a source .of

driving liquid, a plunger arranged in said valve casing for directing driving liquid from said source to said cylinders alternately to advance and retract said. pistons alternately and thereby cause "said arms to impart rotative force tofsaid wheel,

hydraulic -means for reciprocating said plunger, means for directing liquid to said hydraulic means to operate the same and for controlling the operation of said hydraulic means, and a hydraulic detent for preventing said plunger from being moved by the rebound of saidliquid after the same has been moved axially by said means.

16. In a hydraulic' transmission having a plu-- rality of hydraulic motors, the combination of a valve casing connected to said motors and to a 'source of driving liquid, a plunger arranged in said casing for controlling-the delivery of liquid to said motors, a piston and a cylinder arranged at the end of said valve casing for moving said plunger axially to thereby cause liquid to be delivered to said motors alternately, hydraulic means for actuating said piston, means for-directing liquid tosaid hydraulic means to operate the same and for controlling the operation of said hydraulic means. and a4 hydraulic detent for preventing said valve plunger from being moved Aby the rebound of said liquid after the same has been moved axially by said piston.

17. In a hydraulic transmission having a plurality of hydraulic motors, the combination of a i valve casing connected to said motors and to a source of driving liquid, a plunger arranged in said casing for controlling the delivery of liquid to said motors, a piston and a cylinder arranged at each end of said valve casing for moving said plunger axially to thereby cause liquid to be delivered to said motors alternately, means con- 1075v necting said cylinders to a source of liquid for actuating said pistons, -and a spring-pressed check valve communicating with each cylinder and arranged in said meansnto prevent the free return of liquid to said cylin er.

18. The combination, with a source of driving liquid and a hydraulic, motor having a hydraulically operated valve, of a cylinder havinga port near its outer end and a passageway for connecting said port to said source and an auxiliary passageway connecting the inner end of said cylinder to said passageway, a piston arranged in said cylinder for operating said valve and controlling said port, means for directing liquid from said source into said cylinder to advance saidpiston and operate said valve, means for retracting'said piston and thereby expelling liquid from said cylinder through said port until said piston closes said port, a check valve connected in said auxiliary passageway between the inner end of said cylinder and said port for ad- Jmitting driving liquid above a predetermined pressure into the inner end of said cylinder `and `for preventing the escape'of liquid from said vcylinder after said port is closed," and a spring urging said check valve to its seat and preventing 'aid expelled liquid from re-entering said cylinde and thereby serving as adetent for holding said pistonin position.

' WALTER. FERRIS. 

